DIY Exhaust Elbows (Cat 3208 NA)

[Slowmo]

As others have said risers can be a major issue leading to engine failure if you wait too long. The Cat OEM risers are now several thousand dollars, so on my Tolly 40 I ordered Greenwater Marine stainless replacements with a ceramic coating for even more life. They were far less expensive and the yard installing them commented how nicely made they were. They no longer offer water cooled risers, instead using high tech heat blankets. I've used these before and you can put you hand on the exhaust they're so effective.

 

[Aft Deck Capt]

Slowmo, the concern of failure is what prompted me to add the petcock drains as short term insurance. It would be rather disappointing to static lock an engine upon startup....especially if to was to test a new set of risers!

It seems that all aftermarket options while less than Cat are still in the 4K range. Work and home projects have kept me from making any progress for a couple of weeks but I should get the parts ordered soon.

I'm curious as to how hot the spray head gets after it drains at shut down from latent heat in the blanketed portion conducting through the riser. Just thinking about the longevity of the rubber elbows.

 

[Dougcole]

As others have said risers can be a major issue leading to engine failure if you wait too long. The Cat OEM risers are now several thousand dollars, so on my Tolly 40 I ordered Greenwater Marine stainless replacements with a ceramic coating for even more life. They were far less expensive and the yard installing them commented how nicely made they were. They no longer offer water cooled risers, instead using high tech heat blankets. I've used these before and you can put you hand on the exhaust they're so effective.

Greenwater elbows look really nice. I don't understand the concept of a dry riser with a blanket though, how does the hose not melt?

 

[Slowmo]

What is 'dry' is the riser from the manifold the the downturn. At that point the water is sprayed in, just like the OEM with a ring of sprayers. The Cat risers are water jacketed from the exhaust manifold to the spray ring, which keeps them cool but also when they corrode can be a source of water into the engine. So both systems inject water into the exhaust before any rubber pipe is involved. The heat blanket system is simpler and ultimately more reliable. In my old boat this type system has been running for 40 years - and it isn't even stainless. The base price from Greenwater (two months ago) was $3200 for four risers. I added ceramic coathing for $165 each for even longer life (will probably outlive me). The ceramic may not be needed but if you ever run higher sulfer fuel it might help the life.

 

[Slowmo]

I forgot to address the latent heat question. First is the spray ring will cool the connection point. I know others have run these types of risers for years without issues. Keep in mind that the heat capacity of the SS is far less than the old heavy cast iron risers, so even if it is hot, it just doesn't have that much heat capacity to stay hot after shutdown. Also, diesels run excess air so as you throttle down (i.e. to dock), exhaust temps are already declining. As indicated I currently have such a system and over 40 years the only time we had issues with rubber was when the spray nozzle eroded and just delivered a stream of water instead of a spray. Never any issue with latent heat. If you're worried you could put a silcone hose as connector. However, I prefer rubber as you can quickly smell it if it should start to overheat (i.e. if your sprayer isn't working right!)